From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: [PATCH V3] vmx/nmi: Do not use self_nmi() in VMEXIT handler Date: Thu, 28 Feb 2013 12:32:28 +0000 Message-ID: <512F4E5C.8090308@citrix.com> References: <50AE4F8402000078000AAA02@nat28.tlf.novell.com> <50AE41DD.2030703@citrix.com> <50AE511302000078000AAA14@nat28.tlf.novell.com> <50AE46B0.6010807@citrix.com> <50AE590502000078000AAA48@nat28.tlf.novell.com> <50AE4D2C.1040104@citrix.com> <512F384602000078000C1D5B@nat28.tlf.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <512F384602000078000C1D5B@nat28.tlf.novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Jan Beulich Cc: Malcolm Crossley , "Tim (Xen.org)" , "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org On 28/02/13 09:58, Jan Beulich wrote: >>>> On 22.11.12 at 17:12, Jan Beulich wrote: >>>>> On 22.11.12 at 17:05, Andrew Cooper wrote: >>> On 22/11/12 15:55, Jan Beulich wrote: >>>>>>> On 22.11.12 at 16:37, Andrew Cooper wrote: >>>>> A quick solution would be to execute a noop function with >>>>> run_in_exception_handler(). Alternatively, I can code enable_nmi() or >>>>> so which does an inline iret to itself. Which of these would you prefer? >>>> I would actually consider avoiding to run softirqs altogether in that >>>> case, just like native Linux doesn't do any event or scheduler >>>> processing in that case. >>> That would probably be the easiest solution. >>> >>> I was already going to do the same for the rentrant NMI and MCE handling >>> case (and also the process pending upcalls checking), due to the >>> complexities of fixing the race condition at the end of the handler. >>> >>> Unfortunately, I don't think I have time to look at this issue >>> immediately, but if it is ok to wait till the beginning of next week, I >> That's fine of course. > So that was 3 months ago, and we're likely going to need to do > further unfixed releases if this won't move forward. Can you > estimate whether you'll be able to get back to this? > > Jan > With the new enable_nmi() function, I can spin a workaround patch quite quickly, and will try to get that done this week. The remainder of the reentrant tangle is still happening very slowly. ~Andrew